The invention relates to a cap for a pen or pencil that has an opening for the introduction of the pen or pencil and a sealing bead that extends radially inwards and runs around the longitudinal axis of the cap with a closed contour, the cap having at least one first component with a first flexibility and a second component with a second flexibility that is greater than the first flexibility.
A cap of the type specified at the start is disclosed, for example, in U.S. Pat. No. 7,708,486. The cap consists of two components, the first component being comprised of a soft synthetic resin, and the second component being comprised of a hard synthetic resin. In one embodiment both the soft and the hard component each form a region of the inside and a region of the outside of the cap.
In one region of this embodiment, that extends from the closed end of the cap towards its opening up to a cross-over region, the interior of the cap is delimited by the soft component. The soft component is in contact with the pen or pencil in a region of the tip of the pen or pencil and in a region of the shaft. In this way sealed covering of the tip of the pen or pencil is achieved. The hard component extends from the cross-over region towards the closed end of the cap, rests against the soft component and forms a region of the outside. In the region that extends from the opening to the cross-over region the interior of the cap is entirely delimited by the hard component. In the cross-over region where the soft component, extending from the closed end of the cap towards the cross-over region and delimiting the inside, and the hard component, extending from the opening of the cap towards the cross-over region and delimiting the interior, meet, the soft component is guided from the inside towards the outside of the cap and extends further towards the opening, resting against the hard component.
Furthermore, there is formed in the cross-over region on the inside of the cap a sealing bead, made of the hard component and extending inwardly in the radial direction, that locks with a region of the pen or pencil such that inadvertent detachment of the cap from the pen or pencil is prevented.
The manufacture of a cap disclosed by U.S. Pat. No. 7,708,486 requires a complex production method because the soft component must be guided from the inside of the cap to the outside.
Furthermore, this type of cap for sealing pen or pencils that can be sharpened, made of wood, extruded plastic sleeves or wax pencils proves to be inadequate because the outside diameters of these pen or pencils are subject to large tolerance fluctuations ( 15/100 mm). On the one hand these pens or pencils have a large out-of-roundness ( 5/100 mm) due to the production method. On the other hand the outside diameters can increase or decrease with a change in the air humidity. Therefore, not only is the outer form different from pen or pencil to pen or pencil, but it can also change over time. A cap of the type specified at the start then sits on the respective pen or pencil with different degrees of security. Therefore, on the basis of the production tolerance or the climatic conditions the cap can either be hard to place over the pen or pencil or to be pulled off of the latter, or on the contrary, it can inadvertently fall off of the pen or pencil. In this way, when transporting the pen or pencil, for example in a pocket, soiling can occur.
Moreover, by sharpening the pen or pencils manually further irregularities can be produced on the outside of the pen or pencil, and this can make it impossible to produce sufficient contact of the tip with the soft component so as to counter premature drying out.
As a possibility for sealing the tips of pen or pencils with varying outer contours a so-called cone seal was developed. However, this leads to different lengths of the pen or pencil arrangement with the cap placed on it. Moreover, it is a disadvantage of cone seals that they can suddenly become loose because only linear sealing, and no axial coverage, can be produced.
In view of these problems in the prior art, the object underlying the invention is to further develop a cap of the type specified at the start such that the cap enables reliable sealing of the tip of a pen or pencil, in particular of a pen or pencil that can be sharpened, with a changeable outer form, and moreover to provide a simple method of manufacture for the production of this type of cap.
According to the invention this object is achieved in that the interior of the cap in the region lying opposite the opening in relation to the sealing bead and in the region of the sealing bead is delimited by the first component, the second component lies on the outside in the region of the sealing bead along a closed contour on the first component, and the adjustability of the cap by a force acting in the radial direction in the region of the sealing bead is greater than in a region lying opposite the opening in relation to the sealing bead.
The invention can be traced back to the knowledge that a tip of a pen or pencil can be protected against drying out by enclosing it in a diffusion resistant space. With a cap according to the invention this space is formed as follows:
In a state in which the cap sits on the pen or pencil, the tip is enclosed by a space that is delimited by the shaft of the pen or pencil, the sealing bead and the region of the cap that lies opposite the opening in relation to the sealing bead. The region of the cap that lies opposite the opening in relation to the sealing bead and the sealing bead have the first, less flexible component. The flexibility of a component is to be understood as meaning its property of deforming by the effect of an external force. A component with a large degree of flexibility deforms more greatly with the same external force than a component with a small degree of flexibility.
In general, a component with a small degree of flexibility has a higher diffusion resistance than a component with a large degree of flexibility. The diffusion resistance of a component is understood to mean its property of being impermeable to liquids and gases. A component with a high diffusion resistance is less permeable here than a component with a low diffusion resistance. Since the inside of the cap is delimited in the region of the tip by the first component with a small degree of flexibility, this region of the cap therefore has a high diffusion resistance.
By using the first component with a small degree of flexibility in the region of the sealing bead lying opposite the opening the cap is, moreover, stable enough to be able to be grasped well with the hand in this region and be placed on the pen or pencil and be pulled off of it.
In order to guarantee sealed enclosure of the tip of the pen or pencil by means of the first component with the high diffusion resistance the cap has three further properties. First of all, the cap has the sealing bead. The latter runs round the inside of the cap along a closed contour and comprises the first component. If a cap for sealing a pen or pencil with an unchanging outer contour is used, due to a correspondingly formed sealing bead, sealed enclosure of the tip of the pen or pencil can already be guaranteed. Here the sealing bead rests tightly against the shaft of the pen or pencil or locks onto a region of the shaft. With a pen or pencil with a changeable outer contour or outer irregularities a sealing bead on its own is, however, inadequate in order to guarantee permanent sealing of the tip of the pen or pencil.
So that the sealing bead permanently rests tightly against the shaft even on pens or pencils with a changeable outer contour, the adjustability of the cap in the region of the sealing bead is secondly greater than in a region lying opposite the opening in relation to the sealing bead. The adjustability of the cap in a region is understood to mean the property that a wall region located in this region is deflected towards the radial component by a force acting on this region and that has a radial component. This deflection is greater for a region with a large degree of adjustability than for a region with a small degree of adjustability. In general, a component with a small degree of flexibility has a smaller degree of adjustability than a component with a large degree of flexibility.
As will be explained in the following, due to the higher degree of adjustability of the cap in the region of the sealing bead, the sealing bead lies tightly against the shaft of the pen or pencil, and so reliable closure of the tip of the pen or pencil is achieved. According to the invention a minimum inside diameter of the cap in the region of the sealing bead is chosen to be smaller than a minimum outside diameter of the shaft of the pen or pencil in the region which, in the state in which the cap sits on the pen or pencil, should be in contact with the sealing bead. If this type of cap is placed on the pen or pencil, the shaft of the pen or pencil comes into contact with the sealing bead. By means of the adjustability of the cap in the region of the sealing bead the latter is pushed outwards, and every region of a closed contour running round the shaft of the pen or pencil comes into contact with a region of the sealing bead. The inside diameter of the cap in the region of the sealing bead and the adjustability of the cap can be chosen such that this can also be achieved when the shaft has out-of-roundnesses or the diameter or the form of the shaft change over time.
Thirdly, in the region of the sealing bead the cap has a second component lying on the first component on the outside along a closed contour. The second component has a high degree of flexibility and acts like a binding that supports the cap in the region with the greater degree of adjustability. In this way the cap is protected against damage in this region, for example against excessive deflection of the wall region which could lead to the cap breaking. The second component can also additionally press the sealing bead against the shaft of the pen or pencil and further improve the sealing of the tip of the pen or pencil.
Since the second component has a greater degree of flexibility than the first component, it is also softer and offers better grip than the latter. Since the second component forms a region of the outside of the cap, in this region the cap can be gripped well with the fingers, and can also be pulled off of the pen or pencil and placed on it without any problem, even if one has damp or creamy hands.
Therefore, the functionality of the cap is achieved by an appropriate choice of the first and the second component and a sealing bead adapted to the diameter of the pen or pencil, the adjustability in the region of the sealing bead being greater than in the region that lies opposite the opening in relation to the sealing bead. The first component is chosen such that the required stability, dimensional accuracy and diffusion resistance of the cap is achieved. The second component is chosen such that the cap offers good grip and is sufficiently adjustable in the region of the sealing bead. In this way strong, close, air-tight and diffusion resistant closure of the tip of the pen or pencil is achieved. The pen or pencil can thus be protected against premature drying out. The cap can sit securely on the pen or pencil, but can still be easily pulled off. The cap sits securely on the pen or pencil and can be pulled off without excessive exertion. Clearly lower cap pull-off forces can be guaranteed.
According to the invention the first component can comprise a thermoplastic with an elasticity modulus of 1200-2400 N/mm2, preferably ABS or MABS with an elasticity modulus of approximately 2000 N/mm2. According to the invention the second component can comprise a thermoplastic elastomer with a hardness range of 10 ShA-90 ShD, preferably TPE-S or TPE-U with approximately 60 ShA.
In another embodiment of the invention a wall thickness of the first component in the region of the sealing bead can be less than a wall thickness of the region which lies opposite the opening in relation to the sealing bead. A wall thickness is to be understood here to mean an average wall thickness. The wall thickness in the region of the sealing bead and/or in the region that lies opposite the opening in relation to the sealing bead can be a function of the location. However, the wall thickness can also be equal everywhere. By reducing the wall thickness in the region of the sealing bead the adjustability of the first component in the region of the sealing bead can be increased. Furthermore, a saving of the first component, and so a saving of cost can be achieved.
The second component that lies on the outside of the first component has a greater degree of flexibility than the first component. For this reason the adjustability of the cap in the region of the sealing bead in which the wall with the reduced thickness is stabilised by the second component lying on the outside is always greater than in the region of the cap that lies opposite the opening in relation to the sealing bead.
In another embodiment of the invention a maximum wall thickness of the first component can be smaller in the region of the sealing bead than a minimum wall thickness of the first component in the region which lies opposite the opening in relation to the sealing bead. The wall thickness in the region of the sealing bead and/or in the region lying opposite the opening in relation to the sealing bead can be equal everywhere in the corresponding regions. However, it can also be a function of the location. By further reducing the wall thickness in the region of the sealing bead to a minimum value, the adjustability of the cap in this region can be further increased. Moreover, there can thus be further savings on material and costs.
An embodiment in which a notch that does not totally penetrate the first component in the radial direction is formed on the outside of the cap at least in the region of the sealing bead and the second component is positioned in this notch is also advantageous. The notch is formed such that the wall thickness of the first component in the region of the sealing bead is smaller than a minimum wall thickness in the region that lies opposite the opening in relation to the sealing bead. In this way the greater adjustability of the cap in the region of the sealing bead is achieved.
In one embodiment of the invention the second component can be positioned in the notch so that it is aligned with the outside of the first component of the cap in another axial region. In this way the connection of the second component to the first component can be particularly stable with respect to forces acting in the longitudinal direction along the outside of the cap. If, for example, the cap is gripped by the fingers on the soft component and is pulled off of the pen or pencil, the likelihood of the second component being detached from the cap by the effect of this force is reduced. However, the second component can also project from the outside of the first component or be set back from the outside of the first component.
In another possible embodiment the first component and/or the second component can be elastically deformable. In this way the sealing of the tip of the pen or pencil can be additionally improved. Upon placing the cap on the pen or pencil the region of the sealing bead is deflected radially outwards together with the second component running round the outside of the cap. If the first and/or the second component has/have elastic properties, in this way a re-set force pressing the sealing lip tightly and securely against the shaft of the pen or pencil can be brought about. In this way the sealing of the space in which the tip of the pen or pencil is enclosed is additionally increased.
Another advantageous embodiment of the invention is characterised in that the first component and/or the second component extend/s at least partially into a region between the opening and the sealing bead. The interior of the cap in the region between the opening and the sealing bead can be delimited here by the first component. The second component can extend into the region between the opening and the sealing bead. As already mentioned, the more flexible second component offers more grip than the first component. Since the outer region of the cap formed by the second component increases, the grip offered by the cap also improves.
Moreover, it can be advantageous if the first and/or the second component comprise/comprises a plastic. In this way different forms of the cap can be produced inexpensively in a simple manner, for example by an injection moulding technique.
The invention also creates a method of producing a cap of the type specified at the start. Thermoplastics are advantageously used here for the first and the second component. The second component can also be made of silicone that can be processed by injection moulding. The region of the cap made of the first component can be produced by an injection moulding method. If the increased adjustability of the cap in the region of the sealing bead is produced by reducing the wall thickness by means of a notch, this can also already be produced in this procedural step. In a second production step the second component is applied to the first component in a heated state. This leads to re-heating of the first component. Since the second component lies around the first component, in this region it acts like a thermal sleeve. Tempering of the first material takes place, by means of which the latter can acquire greater flexibility.
The production method described above is particularly easy because only two production steps which are based on a known injection moulding method are required in order to produce the cap. A cap according to one embodiment of the invention can thus be produced inexpensively in large quantities.
Within the framework of this disclosure the cap according to the invention should also be protected together with a cosmetic pencil that can be sharpened. The cosmetic pencil can be, for example, a wax pencil. It is difficult to sharpen these pencils and, in addition, they have very out-of-round and varied outside diameters. If the tip of a wax pencil is exposed to air for a long period of time it dries out and the pencil becomes unusable. The tip of a wax pencil easily breaks off if, for example, the pencil falls to the ground. Moreover, soiling caused by wax pencils is difficult to clean. These problems can be eliminated by using a cap according to the invention.